I seriously doubt Stan gets anywhere near 10% of any Marvel movies' gross. I think he does get a few million each year (any info on this, anyone?) from Marvel to be their public spokesperson (and ALWAYS say nice things about them & Disney), promote their products, and do a cameo and be listed as 1 of the Executive Producers on their movies.
I wish I did know the details of how Stan divides any of his non-POWN income between himself & 'POWN the Company'.